Anchors installed in soil (hereinafter referred to as "earth anchors") are commonly utilized to provide support, either in tension or in compression, for electrical or mechanical hardware or equipment. For example, earth anchors are commonly utilized to provide anchorage, in tension, for guy lines used to support electrical transmission, distribution and communication equipment. Earth anchors are also used to provide support, in compression, for electrical and mechanical equipment such as street lighting poles, pipelines, and other similar equipment.
Earth anchors typically include a helix formed in a spiral configuration around a hub. When the earth anchor is to be installed into the earth, a torque tube is coupled to the hub of the earth anchor so that the torque applied to the torque tube is transferred through the hub from the torque tube to the helix. The torque tube is controlled to then apply both a downward force and a rotational force to the earth anchor. The combination of the downward and rotational forces causes the helix to bore into the earth.
The size and weight of the equipment supported by an installed earth anchor determine the load on that earth anchor. Since it is primarily the helix of the earth anchor which absorbs the load exerted on the earth anchor, the diameter of the helix must be designed to withstand its expected load. The compaction of the earth into which the earth anchor is installed also determines the diameter of the helix. That is, for a given load, the diameter of a helix can be made smaller for soils which are more compact. Furthermore, the size of the helix and the compaction of the soil into which the earth anchor is installed determine the amount of torque required to install the earth anchor. Since it is the function of the hub to transfer torque from the torque tube to the helix during installation of the earth anchor, it is the size and weight of the hub which determine the amount of the torque which can be applied to the hub and transferred from the torque tube to the helix.
Because the equipment supported by earth anchors varies in size and weight, and because the compaction of the earth varies from location to location, the helices of earth anchors have been historically provided in a variety of sizes and weights. Because the helices of earth anchors are provided in a variety of sizes and weights, and because the compaction of the earth varies from location to location, the hubs of earth anchors have also been historically provided in a variety of sizes and weights.
For example, an earth anchor requiring 8,000 foot pounds of torque to install the earth anchor into the earth was provided with a 11/2 inch square hub whereas an earth anchor requiring 12,000 foot pounds of torque was provided with a 2 inch square hub. A hub having a standard, intermediate size and weight but which can be used over a wide range of torques results in cost savings due both to this standardization of hubs and to the elimination of the higher cost, more massive hubs which were heretofore used in the upper portion of this torque range.